1. Field of the Invention
This invention generally relates to a bicycle front derailleur that is fastened to the bicycle frame. More specifically, the present invention relates to a mounting fixture for mounting the bicycle front derailleur to a tubular member of the bicycle frame in a manner such that the angular position of the bicycle front derailleur can be finely adjusted relative to an axis that is parallel to a center axis of the tubular member of the bicycle frame.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. Recently, bicycle frames have been extensively redesigned. One component that has been extensively redesigned is the bicycle frame and the mounting structures
A bicycle front derailleur is sometimes attached to the seat tube (tubular member) of the bicycle frame by a mounting fixture, which is fastened by being welded or screwed to the seat tube of the frame. This mounting fixture is sometimes called a direct-mounting seat. Since such mounting fixtures are fastened to the seat tube beforehand, the chain guide of the derailleur cannot be disposed in a parallel position directly above the front sprocket in the case of systems in which a band is formed as an integral part of the front derailleur, unless the orientation is adjusted about an axis parallel to the seat tube following mounting.
The present invention relates to a front derailleur which is fastened to a bicycle frame and which can be attached to a mounting fixture having a circular arcuate surface so that fine adjustments can be made by rotation about a first axis, and also relates to this mounting fixture.
In the past, therefore, mounting fixtures have included fittings devised so that not only the vertical position can be adjusted, but also the rotation about the axis can be adjusted (e.g., see Japanese Patent Application Laid-Open No. 62-177594). This conventional mounting fixture has a bicycle frame fastening part which is fastened with the aid of a screw to the seat tube, and also has a front derailleur mounting part which is disposed on the bicycle frame fastening part and which can be fastened so that fine adjustments are possible by rotation about a first axis in a position distant from the seat tube. The front derailleur mounting part is integrally formed by being bent from the bicycle frame fastening part. Long slots are formed at this location above and below, and the front derailleur mounting part has a first fine adjustment washer which has a circular arcuate protruding surface used for fine adjustment and disposed on the front surface of the slot, and a second fine adjustment washer which has a circular arcuate recessed surface in contact with the first fine adjustment washer. Fastening bolts are passed through these two washers and slots, and are screwed into the front derailleur along the forward-rearward direction, so that the front derailleur can be finely adjusted by rotation about the first adjustment axis. Furthermore, in order to maintain the finely adjusted state about the first adjustment axis, a contact bolt having the configuration of a set screw with a recessed hexagonal socket in contact with the root portion of the front derailleur mounting part bent from the bicycle frame fastening part is disposed in the front derailleur.
When a front derailleur is mounted on such a mounting fixture, the mounting fixture is threadedly fastened to the seat tube in a specified position, and the front derailleur is then fastened in place by the fastening bolt after the vertical position and orientation about the first adjustment axis have been adjusted. In this state, the contact bolt is brought into contact with the front derailleur mounting part so that the adjusted state is maintained. The orientation of the front derailleur about the first adjustment axis therefore tends not to vary even if a force should act on the front derailleur from the chain toward the seat tube during gear shift.
A contact bolt that is disposed in parallel in a position in close proximity to the fastening bolt is used in the abovementioned conventional mounting fixture in order to maintain the adjusted orientation after of the front derailleur about the first adjustment axis. Consequently, a large force is caused to act on the contact bolt by the torque that is generated by the chain, so that there is a danger that the adjusted orientation will vary because of a slight looseness of the screw or the like.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved mounting fixture. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.